Evaluation of the preform design of a stepped forging part by coupled thermoviscoplastic finite-element analysis and visioplasticity

To achieve a sound product without lap defects, both finite-element analysis and the visioplasicity technique were adopted in this article as a design tool to execute the preform design of a stepped forging part, which is a simplified model to simulate one piece of a five-finger-span part applied widely in the bicycle industry. The physical modelling of the real material, performed by visioplasticity for four sets of preliminary preform designs, was performed first. Subsequently, one of the preliminary preforms was simulated numerically using the rigid-viscoplastic finite-element method under both uncoupled and coupled thermomechanical conditions. It was seen that the numerical results evaluated by the finite-element method were consistent with the experimental data obtained by visioplasticity. Moreover, the lap defect, as well as a local high-effective-strain condition due to improper design of the preform geometry, were observed by both visioplasticity and finite-element analyses. Consequently, four sets of re-designed preforms were evaluated numerically in the coupled thermomechanical condition, and the optimal preform design obtained. Finally, the rules for improving the preform design of a stepped forging were proposed and discussed.